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PCM Cellulose Wall Technologies



Description Of Wall

During 2004, the Oak Ridge National Laboratory (ORNL) established a research team for development of a new type of cellulose fiber insulation, which can thermally perform as a massive component of a building envelopes. Since the beginning, this project has been a joint effort involving Advanced Fiber Technology (AFT), a producer of the cellulose insulation, BASF, a global producer of phase change materials (PCM), and the ORNL Buildings Envelopes Program.

Figure 1. Application of the cellulose-PCM mixture into the test wall.

We expect that a new generation of PCM-enhanced cellulose insulation would have a high potential for successful adoption by the US building market due to:

• Reduction of space conditioning energy consumption

• Reduction of peak loads, resulting in smaller and less costly energy conversion

and distribution equipment

• Improvement of the occupant comfort

• Compatibility to traditional wood and steel framing technologies used in

residential and small commercial buildings

• Potential for application in retrofit projects

Now, this new insulation material is almost ready for the market introduction. During 2005/05 PCM-enhanced cellulose was experimentally validated with the use of dynamic hot box tests of attic and wall assemblies, and in several small-scale field applications. During 2007 ORNL, AFT, BASF, and Building America teams will jointly perform full-scale, whole-house demonstrations in different US climates. Several fiber insulation companies have already expressed their interests in licensing this technology.

Waste paper
Packaging process

Figure 2. Production process of cellulose insulation.

To reduce project costs, for the research purposes, small amounts of different cellulose-PCM blends were produced using the AFT pilot line. Using this small-scale facility, the ORNL team was able to produce insulations with different amounts of PCM added to the cellulose fibers. As shown on the Figure 3, the pilot line is a miniature of the full-scale production facility. On the pilot line, all components were separately measured and manually added to the cellulose.

In this project, microencapsulated PCM –Micronal 5001X produced by BASF was utilized. Micronal is produced with the use of a new micro-encapsulation technology that holds microscopic wax droplets inside hard acrylic polymer shells. The small, 2 to 20 micrometer sized microcapsules melt at 78.5 ºF (25.8 ºC) . Since production of cellulose insulation already includes the addition of dry chemicals, the addition of a dry PCM component doesn’t require significant changes in the manufacturing or packaging processes.

AFT pilot line for cellulose production
Addition of PCM to cellulose

Figure 3. AFT Pilot Line for Production of Cellulose Test Fiber Material

Introduction of fire from the standard cigarette
Cross section of the burned sample of cellulose insulation containing PCM

Figure 4. Smoldering Combustion Tests (ASTM C-739) of the Cellulose-PCM Blend

Cellulose insulation with added PCMs, like conventional cellulose insulation, must demonstrate resistance to smoldering combustion and pass other flammability tests. During 2005, a series of the Smoldering Combustion Tests ASTM C-739 (2004) were performed on specimens of cellulose insulation containing 5% to 30% of microencapsulated PCM. As shown of Figure 4, fire was introduced to the test specimens using a cigarette as the ignition source. This test method is for the determination of smoldering combustion resistance for cellulose insulations. All cellulose- PCM blends passed the ASTM C-739 test – in all specimens less than 1% loss of the mass of the cellulose insulation was observed. The pass/fail requirement is less that 15 wt % loss in mass as a result of the test.

The addition of dry PCM can be accomplished on existing manufacturing lines where other dry chemicals are added. As shown on the Figure 5, amounts of PCM can be monitored with the use of a Scanning Electron Microscope (SEM).

Cellulose without PCM - visible fire-retardant chemicals.
Cellulose with added 30% of PCM – visible clusters of PCM pellets

Figure 5. Scanning Electron Microscope Images of Cellulose Insulation


During 2005/05 we tested this new material for wall and attic applications. The ORNL Buildings Technology Center team prepared14x 14-ft model of the residential attic, and 8x8-ft wood-framed wall containing cellulose insulation. These test specimens were later utilized for dynamic hot-box testing. Figure 6 shows ORNL test attic with PCM-enhanced cellulose insulation.

Figure 6. ORNL test attic with PCM-enhanced cellulose insulation.

The test wall was constructed with nominal 2x6-inch studs installed on 16-inch spacing. Three wall cavities were insulated with conventional cellulose at a density of about 2.6 lb/ft 3 (41.6-kg/m 3). Three wall cavities were insulated with a cellulose-PCM blend of the same density that contained 22 wt. % PCM. It is estimated that about 38-lb (17-kg) of PCM-enhanced cellulose insulation (containing 8-lb or 3.6-kg of PCM) was used for this dynamic experiment.

At the beginning of the measurement, temperatures were stabilized at about 65 ºF (18.3 ºC) on the cold side and 72 ºF (22.2 ºC) on the warm side. Next, temperature of the worm side was rapidly increased to 110 ºF (43.3 ºC). Test-generated heat flux results are shown in Figure 7 for both sides of the wall.

Figure 7. Cellulose-PCM Insulation Installed on the Wall Specimen Utilized for Dynamic

It took 15 hours to fully charge the PCM material within the wall. Heat fluxes on both sides of the wall were measured and compared. The most important finding of this experiment was that PCM-enhanced cellulose really works in truly full-scale conditions. It can help in reduction of the peak-hour thermal load by about 40%.

At the present time ORNL team works on series of dynamic simulations helping in optimization of the amount of PCM for residential attic and wall applications.

For more information please contact Dr. Jan Kosny


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